PRIMECLUSTER Global File Services Configuration and Administration Guide 4.1 (Linux)

12.1.1 Amount of Cache

It is possible to tune the following items:

• Amount of extent-based management information to be cached in memory
  (SFCFS_NCACHE_EXTENT)
• Amount of directory information to be cached in memory
  (SFCFS_NCACHE_DIRECTORY)
• Number of i-nodes on the disk to be cached in memory
  (SFCFS_NCACHE_INODE)

   

These values can be specified using sfcadm(8).

For each file system, an area with a size equal to the specified value x 1 kilobytes is reserved for the extent-based management information and for the directory information, and an area with a size equal to the specified value x 4 kilobytes is reserved for i-nodes. All of these areas are in the MDS process space.

By the default, 8 megabytes (8192) of memory is secured as 10 megabytes (10240) and an i node as 2 megabytes (2048) and directory information as extent management information.

If the size of a directory exceeds directory cash size, the performance of the file creation to the directory or reference will fall. When the directory where size is big may be created, it recommends strongly setting up the amount of cash of directory information greatly.

Use sfcstat(8), the statistics command specific to the GFS Shared File System, to determine the cache hit ratios for the items above and perform tuning if necessary.

 

(Example)

# sfcadm -o SFCFS_NCACHE_EXTENT=4096 /dev/sfdsk/gfs/dsk/volume1
# sfcadm -o SFCFS_NCACNE_DIRECTORY=20480 /dev/sfdsk/gfs/dsk/volume1
# sfcadm -o SFCFS_NCACHE_INODE=5120 /dev/sfdsk/gfs/dsk/volume1